An audio relationship between two or more microphones may be used in multi-microphone speech processing applications, such as hearing devices (e.g., headphones, hearing assistance devices). In processing audio signals from two or more sources, some existing beamformers are designed based on simple geometric considerations based on assumptions about the relationship between audio sources. For example, some existing solutions assume that a target speaker is located directly to the front of a hearing device, and assume that the speech signal received is identical at the two microphones on each side of the hearing device. The assumptions made by existing solutions do not adapt to movement, to external noise interference, or other changes in the acoustic environment. It is desirable to improve multi-microphone speech processing.